Suppressing phase segregation in bromide-containing perovskite films via compositional engineering for indoor applications

Although the bandgap tunability of perovskite films makes them promising for indoor applications of perovskite solar cells (PSCs), bromide-containing wide-bandgap perovskite films often suffer from phase segregation. In this study, we explored phase-segregation-free wide-bandgap perovskite films through compositional engineering. We revealed that increasing the Cs ratio stabilizes triple-cation wide-bandgap perovskite films. Furthermore, we demonstrated that chloride can be incorporated into bromide-containing perovskite films, thereby enhancing their stability under light irradiation. Cs-rich, chloride-containing triple-cation perovskite films exhibited minimal phase segregation under AM1.5G 100 mW cm^-2irradiation. These results indicate that the proposed films are promising not only for indoor applications, but also for tandem solar cells. PSCs employing the Cs-rich, chloride-containing perovskite as the light absorber were fabricated after optimizing the film fabrication process. The PSCs showed power conversion efficiency of 31.1% under 1000 lx LED illumination.